controling electrical appliances through tv remote

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1. INTRODUCTION

Objective:

The main aim of this embedded application is to control electrical appliances using TV

Remote.

Description:

An embedded system is some combination of computerhardware and software, either fixed in c

apability or programmable, that is specifically designed for a particular function. Since the embedded

system is dedicated to specific tasks, design engineers can optimize it reducing the size and cost of the

product and increasing the reliability and performance. IR remote acts as the transmitter in this project.

When a button is pressed in the remote, the signal will be passed and received by the IR receiver

TSOP Receiver.

Many household tasks were automated by the development of special appliances. For instance,

automatic washing machines were developed to reduce the manual labor of cleaning clothes,

and water heaters reduced the labor necessary for bathing. Other traditional household tasks, like food

preservation and preparation have been automated in large extent by moving them into factory

settings, with the development of pre-made, pre-packaged foods, and in some countries, such as the

United States, increased reliance on commercial food preparation services, such as fast

food restaurants. Volume and the factory setting allows forms of automation that would be impractical

or too costly in a home setting. Standardized foods enable possible further automation of handling the

food within the home.

A home automation system integrates electrical devices in a house with each other. The

techniques employed in home automation include those in building automation as well as the control

of domestic activities, such as home entertainment systems, houseplant and yard watering, pet feeding,

changing the ambiance "scenes" for different events (such as dinners or parties), and the use

of domestic robots. Devices may be connected through a computer network to allow control by

a personal computer, and may allow remote access from the internet. Through the integration

of information technologies with the home environment, systems and appliances are able

to communicate in an integrated manner which results in convenience, energy efficiency, and safety

benefits.


2. BLOCK DIAGRAM

Fig 2.1: Block Diagram

3. HARD WARE DESCRIPTIONS


3.1 TV REMOTE

Fig 3.1.1: TV Remote

A remote control is a component of an electronics device, most commonly a television, used

for operating the device wirelessly from a short line distance. The remote control can be contracted

to remote or controller.

Itis known by many other names as well, such as converter clicker,didge, flipper, the tuner, the change

r, or the button. Commonly, remote controls are Consumer IR devices used to issue commands from a

distance to televisions or other consumer electronics such as stereo systems, DVD players and

dimmers. Remote controls for these devices are usually small wireless handheld objects with an array

of buttons for adjusting various settings such as television channel, track number, and volume. In fact,

for the majority of modern devices with this kind of control, the remote contains all the function

controls while the controlled device itself only has

a handful of essential primarycontrols. Most of these remotes communicate to their respective devices

via infrared (IR) signals and a few via radio signal.

Television IR signals can be mimicked by a universal remote, which is able to

emulate the functionality of most major brand television remotecontrols.


3.2Sensor

A sensor (also called detectors) is a device that measures a measurable attribute and converts it

into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass

thermometer converts the measured temperature into expansion and contraction of a liquid which can

be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which

can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.

Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and

lamps which dim or brighten by touching the base. There are also innumerable applications for sensors

of which most people are never aware. Applications include cars, machines, aerospace, medicine,

manufacturing and robotics.

Fig 3.2.1: Sensors

INFRARED SENSOR

An infrared sensor is an electronic device that emits and/or detects infrared radiation in order

to sense some aspect of its surroundings. Infrared sensors can measure the heat of an object, as well as

detect motion. Many of these types of sensors only measure infrared radiation, rather than emitting it,

and thus are known as passive infrared (PIR) sensors. All objects emit some form of thermal radiation,

usually in the infrared spectrum. This radiation is invisible to our eyes, but can be detected by

an infrared sensor that accepts and interprets it. In a typical infrared sensor like a motion detector,

radiation enters the front and reaches the sensor itself at the center of the device. This part may be


composed of more than one individual sensor, each of them being made from pyroelectric materials,

whether natural or artificial. These are materials that generate an electrical voltage when heated or

cooled. These pyroelectric materials are integrated into a small circuit board. They are wired in such a

way so that when the sensor detects an increase in the heat of a small part of its field of view, it will

trigger the motion detector's alarm. It is very common for an infrared sensor to be integrated into

motion detectors like those used as part of a residential or commercial security system

Most motion detectors are fitted with a special type of lens, called a Fresnel lens, on the

sensor face. A set of these lenses on a motion detector can focus light from many directions, giving

the sensor a view of the whole area. Instead of Fresnel lenses, some motion detectors are fitted with

small parabolic mirrors which serve the same purpose. An infrared sensor can be thought of as a

camera that briefly remembers how an area's infrared radiation appears. A sudden change in one area

of the field of view, especially one that moves, will change the way electricity goes from the

pyroelectric materials through the rest of the circuit. This will trigger the motion detector to activate an

alarm.

If the whole field of view changes temperature, this will not trigger the device. This makes it

so that sudden flashes of light and natural changes in temperature do not activate the sensor and cause

false alarms. Infrared motion detectors used in residential security systems are also desensitized

somewhat, with the goal of preventing false alarms. Typically, a motion detector like these will not

register movement by any object weighing less than 40 pounds (18 kg). With this modification,

household pets will be able to move freely around the house without their owners needing to worry

about a false alarm. For households with large pets, sensors with an 80-pound (36 kg) allowance are

also made.


Fig 3.2.2: Infrared Sensor

INTRODUCTION TO IR

One of the advantages of infrared remote is that there is no radio signal for crooks to monitor

and record for use against you later on. Instead, there is a beam of invisible infrared light which comes

from a standard hand-held remote control unit. So from that point of view, it is pretty secure. There is,

though, an enormous variety of tasks to which you could put the unit. Just think of the myriad of

things in your home these days which use infrared remote to turn things on and off, change levels,

open and close.

WHAT IS INFRARED?

Infrared is a energy radiation with a frequency below our eyes sensitivity, so we cannot see it.

Even that we cannot "see" sound frequencies, we know that it exist, we can listen them.

Fig 3.2.3: Infrared Radiation


Even that we cannot see or hear infrared, we can feel it at our skin temperature sensors. When you

approach your hand to fire or warm element, you will "feel" the heat, but you can't see it. You can see

the fire because it emits other types of radiation, visible to your eyes, but it also emits lots of infrared

that you can only feel in your skin.

INFRARED IN ELECTRONICS

Infra-Red is interesting, because it is easily generated and doesn't suffer electromagnetic

interference, so it is nicely used to communication and control, but it is not perfect, some other light

emissions could contains infrared as well, and that can interfere in this communication. The sun is an

example, since it emits a wide spectrum or radiation. The adventure of using lots of infra-red in

TV/VCR remote controls and other applications, brought infra-red diodes (emitter and receivers) at

very low cost at the market.

From now on you should think as infrared as just a "red" light. This light can means something to the

receiver, the "on or off" radiation can transmit different meanings. Lots of things can generate

infrared, anything that radiate heat do it, including out body, lamps, stove, oven, friction your hands

together, even the hot water at the faucet.

To allow a good communication using infra-red, and avoid those "fake" signals, it is

Imperative to use a "key" that can tell the receiver what is the real data transmitted and what is fake.

As an analogy, looking eye naked to the night sky you can see hundreds of stars, but you can spot

easily a far away airplane just by its flashing strobe light. That strobe light is the "key", the "coding"

element that alerts us.

Similar to the airplane at the night sky, our TV room may have hundreds of tinny IR sources,

our body, and the lamps around, even the hot cup of tea. A way to avoid all those other sources, is

generating a key, like the flashing airplane. So, remote controls use to pulsate its infrared in a certain

frequency. The IR receiver module at the TV, VCR or stereo "tunes" to this certain frequency and

ignores all other IR received. The best frequency for the job is between 30 and 60 kHz, the most used

is around 36 kHz.

So, remote controls use the 36 kHz (or around) to transmit information. Infrared light emitted

by IR Diodes is pulsated at 36 thousand times per second, when transmitting logic level "1" and

silence for "0".


IR GENERATION

To generate a 36 kHz pulsating infrared is quite easy, more difficult is to receive and identify

this frequency. This is why some companies produce infrared receives, that contains the filters,

decoding circuits and the output shaper, that delivers a square wave, meaning the existence or not of

the 36kHz incoming pulsating infrared.

It means that those 3 dollars small units, have an output pin that goes high (+5V) when there is a

pulsating 36kHz infrared in front of it, and zero volts when there is not this radiation.

Fig 3.2.4: IR generations

A square wave of approximately 27uS (microseconds) injected at the base of a transistor, can

drive an infrared LED to transmit this pulsating light wave. Upon its presence, the

commercial receiver will switch its output to high level (+5V).

If you can turn on and off this frequency at the transmitter, your receiver's output will indicate when

the transmitter is on or off.

Those IR demodulators have inverted logic at its output, when a burst of IR is sensed it drives its

output to low level, meaning logic level = 1.


Fig 3.2.5: IR logic levels

The TV, VCR, and Audio equipment manufacturers for long use infra-red at their remote

controls. To avoid a Philips remote control to change channels in a Panasonic TV, they use different

codification at the infrared, even that all of them use basically the same transmitted frequency, from 36

to 50 kHz. So, all of them use a different combination of bits or how to code the transmitted data to

avoid interference.

RC-5:

A key feature of RC5 is the use of data-dependent rotations; one of the goals of RC5 was to

prompt the study and evaluation of such operations as a cryptographic primitive. RC5 also consists of

a number of modular additions and exclusive OR (XOR)s. The general structure of the algorithm is

a Feistel-like network. The encryption and decryption routines can be specified in a few lines of code.

The key schedule, however, is more complex, expanding the key using an essentially one-way

function with the binary expansions of both e and the golden ratio as sources of "nothing up my sleeve

numbers". The tantalizing simplicity of the algorithm together with the novelty of the data-dependent

rotations has made RC5 an attractive object of study for cryptanalysts. The RC5 is basically denoted

as RC5-w/r/b where w=word size in bits, r=number of rounds, b=number of 8-bit byte in the key.

Various remote control systems are used in electronic equipment today. The RC5 control protocol is

one of the most popular and is widely used to control numerous home appliances, entertainment

systems and some industrial applications including utility consumption remote meter reading, contact-

less apparatus control, telemetry data transmission, and car security systems. Philips originally

invented this protocol and virtually all Philips’ remotes use this protocol. Following is a description of

the RC5.

When the user pushes a button on the hand-held remote, the device is activated and sends

modulated infrared light to transmit the command. The remote separates command data into packets.

Each data packet consists of a 14-bit data word, which is repeated if the user continues to push the

remote button. The data packet structure is as follows:

2 start bits,

1 control bit,


5 address bits

6 command bits.

The start bits are always logic ‘1’ and intended to calibrate the optical receiver automatic gain

control loop. Next, is the control bit. This bit is inverted each time the user releases the remote button

and is intended to differentiate situations when the user continues to hold the same button or presses it

again. The next 5 bits are the address bits and select the destination device. A number of devices can

use RC5 at the same time. To exclude possible interference, each must use a different address. The 6

command bits describe the actual command. As a result, a RC5 transmitter can send the 2048 unique

commands. The transmitter shifts the data word, applies Manchester encoding and passes the created

one-bit sequence to a control carrier frequency signal amplitude modulator. The amplitude modulated

carrier signal is sent to the optical transmitter, which radiates the infrared light. In RC5 systems the

carrier frequency has been set to 36 kHz. Figure below displays the RC5 protocol


Fig 3.2.6: RC 5 Wave forms

DECODING IR SIGNAL WITH A MICROCONTROLLER


To receive this signal using a microcontroller follows the timing from the figure below. Note

that the Infrared Receiver invert the bit signal, low level means bit ON.

Fig 3.2.7: Decoding IR Signal

During inactivity (no Infrared present) the output of the Infrared receiver is UP (bit zero). You

can connect the IR receiver output to any input port pin or interrupt pin of your microcontroller, and

keep polling it or prepare the interrupt routine to trigger your reading after the first low level sensed.

When you press a key at the remote, it transmits the train of pulses, and your microcontroller will

receive bit #1 first. It will be sensed right after the middle of the bit when it changes from high to low

level to means bit "1". This is the first time that your microcontroller will "see" the incoming IR

signal. You don't need to decode those first two bits, not even the CHK bit (except if you want to

control as the TV do and described above), so you can skip those 3 bits and start to receive the

ADDRESS bits. To do that, you need to skip 2.75 bits time, and you will be exactly at the middle of

the right level of the first ADDRESS bit to be read (non inverted level).

So,

upon sensing the first low level, your software should wait 4.752 milliseconds and then start to read

the next 11 bits spaced 1.728ms each. The first 5 bits are Address and the next 6 bits are Command,

logic correct level, LOW = 0, HIGH = 1. At your bit reading routine use an available microcontroller

port pin and generate a fast pulse UP and DOWN, then use one scope channel to display this pulse,

and the other scope channel to show the incoming signal from the receiver. Press and hold key

number ZERO at the remote, and sync the scope to show a complete wave form, don't worry with

timing. The fast 11 pulses should always be in place of those RED down arrows at the figure. It means

that the "bit reading" software routine will reading exactly in the middle of the correct bit level.


Fig 3.2.7: Correct level of First Address Bit

Your software will need to have two timing delays, the first to wait 4.752ms and the second to

wait 1.728ms. Adjust the timing loop from the 4.752ms until the first fast pulse happens exactly as

indicated above. Then adjust the 1.728 ms timing delay in such way that the last fast pulse (#11) bit

reading happens exactly at the middle of the low part of the last bit (#14).

Check all other bits and fast pulses, they should be all matching ok. Small errors would be

accepted since the reading would be happening in the middle of the bit, few errors for more or less is

not a problem, but it is better to be the most possible in the middle of the low level of each bit. This is

why you should adjust your 1.728ms timing routine looking at the last data bit and fast pulse, if they

match somehow ok, all the other bits should be ok too. Remember that any other remote key will

generate a different pattern and it can confuse you. Use always key number ZERO for this software

calibration.

Once you find the correct timing delays, you can replace the FAST pulse instructions with

NOPS (check your chip instruction set to keep the same clock count wasted), or keep the fast pulse

there just for fun, so you will be able to recheck it in case of problems.

Here few examples of the complete waveform (14 bits) at the Receiver Output:


Fig 3.2.8: Right commands in hexadecimal

Red: AGC pulses (ON)

Blue: Check bit (flipping)

White: Address (00)

Green: Command

3.3 IR RECEIVER

TSOP:

The TSOP17... – Series are miniaturized receivers for infrared remote control systems. PIN

diode and preamplifier are assembled on lead frame, the epoxy package is designed as IR filter.

The demodulated output signal can directly be decoded by a microprocessor. TSOP17.. is the standard

IR remote control receiver series, supporting all major transmission codes.

Features

Photo detector and preamplifier in one package

Internal filter for PCM frequency

Improved shielding against electrical field disturbance


TTL and CMOS compatibility

Output active low

Low power consumption

High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Suitable burst length .10 cycles/burst

Fig 3.3.1: Block diagram of IR receiver

Fig 3.3.2: Application circuit of IR receiver

Description

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The TSOP17... – series are miniaturized

PIN diode and preamplifier are assembled on lead frame, the epoxy package is designed as IR filter.

The demodulated output signal can directly

IR remote control receiver series, supporting all major transmission codes.

Features:


Internal filter for PCM frequency


TTL and CMOS compatibility

Output active low

Low power consumption



Suitable burst length 10 cycles/burst


miniaturized receivers for infrared remote control

preamplifier are assembled on lead frame, the epoxy package is designed as IR filter.

directly be decoded by a microprocessor. TSOP17... is the standard

es, supporting all major transmission codes.

Fig 3.3.3: TSOP





Suitable burst length 10 cycles/burst

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control systems.

preamplifier are assembled on lead frame, the epoxy package is designed as IR filter.

a microprocessor. TSOP17... is the standard


Absolute Maximum Ratings: Tamb = 25C

Parameter Test Conditions Symbol Value Unit

supply voltage (Pin 2) Vs -0.3…6.0 V

supply current (Pin 2) Is 5 mA

Output voltage (Pin 3) Vo -0.3…6.0 V

Output current (Pin 3) Io 5 mA

Junction

temperature

Ti 100 C

Storage

Temperature

Range

Tstg -25…+85 C

Operating

Temperature

Range

Tamb -25…+85 C

Power

consumption

(Tamb < 85C) Ptot 50 mW

Soldering

Temperature

T<10s, 1 mm for

case

Tsd 260 C

Basic Characteristics

Tamb = 25C

Parameter Test

Conditions

Symbol Min Typ Max Unit

Supply

current

Vs=5 V, Ey=0

VS=5 V, Ey=

40 kbx, sun

light

Isd

Ish

0.4 0.6

1.0

1.5 mA

mA

Supply

voltage

Vs 4.5 5.5 V

Transmission Ev=0, test D 35 M


distance signal see

fig.7,

IR diodes

TSAL6200,

If=400mA

Output

Voltage Low

(Pin 3)

IOSL = 0.5

mA,Ee = 0.7

mW/m2

f = fo, tp/T =

0.

VOSL

250 m V

Irradiance

(30 – 40 kHz

Pulse width

tolerance:

Tpi – 5/fo <

tpo < tpi +

6/fo,

test signal

(see fig.7

Ee min

0.35 0.5 mW/m2

Irradiance

(56 kHz)

Pulse width

tolerance:

Tpi – 5/fo <

tpo < tpi +

6/fo,

test signal

(see fig.7

Ee min 0.4 0.6 mW/m2

Irradiance Tpi – 5/fo <

tpo < tpi+ 6/fo

Ee max 30 W/m2

Directivity Angle of half

transmission

distance

�1/2 4.45 deg


TSOP 17…. Series Photo modules are miniature IR sensor modules with PIN photodiode and a

preamplifier stage enclosed in an epoxy case. Its output is active low and gives +5 V when off. The

demodulated output can be directly decoded by a microprocessor. The important features of the

module includes internal filter for PCM frequency, TTL and CMOS compatibility, low power

consumption (5 volt and 5 mA), immunity against ambient light, noise protection etc. The added

features are continuous data transmission up to 2400 bps and suitable burst length of 10 cycles per

burst.

The photo module has a circuitry inside for amplifying the coded pulses from the IR

transmitter. The front end of the circuit has a PIN photodiode and the input signal is passed into an

Automatic Gain Control(AGC) stage from which the signal passes into a Band pass filter and finally

into a demodulator. The demodulated output drives an NPN transistor. The collector of this transistor

forms the output at pin3 of the module. Output remains high giving + 5 V in the standby state and

sinks current when the PIN photodiode receives the modulated IR signals.

Design considerations

For the proper functioning of the Photo module, it is necessary to consider some important

aspects.

1. Supply voltage should be + 5 Volts. For this, a 5.1 volt Zener must be connected to the +V pin and

ground.

2. A 100 uF capacitor should be connected to the +V pin as a buffer and filter capacitor. This will

suppress the power supply disturbances.

3. Carrier frequency should be close to the center frequency of the band pass filter.38 kHz in the case

of TSOP 1738.

4. Burst length must be 10 cycles per burst or more.

5. Between each 10 to 70 cycles, a gap time of 14 cycles is necessary to reset the module.


6. DC lights such as tungsten bulb and daylight affects the functioning of the photo module.

7. Signals from Fluorescent lamps with electronic ballast will affect the working of the photo module.

8. Continuous IR signal (non- pulsed) will disturb the photo module and it will not responds to it.

Suitable Data Format

The circuit of the TSOP17 is designed in that way that unexpected output pulses due to noise or

disturbance signals are avoided. A band pass filter, an integrator stage and an automatic gain control

are used to suppress such disturbances. The distinguishing mark between data signal and disturbance

signal are carrier frequency, burst length and duty cycle. The data signal should fulfill the following

condition: • Carrier frequency should be close to center frequency of the band pass (e.g. 38 kHz).

• Burst length should be 10 cycles/burst or longer.

• After each burst which is between 10 cycles and 70 cycles a gap time of at least 14 cycles is

necessary.

• For each burst which is longer than 1.8ms a corresponding gap time is necessary at some time in the

data stream. This gap time should have at least same length as the burst.

• Up to 1400 short bursts per second can be received continuously.

Some examples for suitable data format are: NEC Code, Toshiba Mincom Format, Sharp Code, RC5

Code, RC6 Code, R–2000 Code, Sony Format (SIRCS). When a disturbance signal is applied to the

TSOP17... it can still receive the data signal. However the sensitivity is reduced to that level that no

unexpected pulses will occur. Some examples for such disturbance signals which are suppressed by

the TSOP17... Are:

• DC light (e.g. from tungsten bulb or sunlight)

• Continuous signal at 38 kHz or at any other frequency

• Signals from fluorescent lamps with electronic ballast (an example of the signal modulation is in the

figure below).


Fig 3.3.4: IR Signal from Fluorescent Lamp with low modulation

IN 4007

Features:

Diffused Junction

High Current Capability and Low Forward

Voltage Drop

Surge Overload Rating to 30A Peak

Low Reverse Leakage Current

Plastic Material: UL Flammability

Classification Rating 94V-0

APPLICATION:

Single phase, half wave, 50Hz, and resistive or inductive load.

For capacitive load, debate current by 20%.

Forward Voltage Drop, Vf


Notice that the diode conducts a small current in the forward direction up to a threshold

voltage, 0.3 for germanium and 0.7 for silicon ; after that it conducts as we might expect. The forward

voltage drop, Vf, is specified at a forward current, If.

Leakage current

In the reverse direction there is a small leakage current up until the reverse breakdown voltage

is reached. This leakage is undesirable, obviously the lower the better, and is specified at a voltage less

the than breakdown; diodes are intended to operate below their breakdown voltage.

Current Rating

The current rating of a diode is determined primarily by the size of the diode chip, and both

the material and configuration of the package, Average Current is used, not RMS current. A larger

chip and package of high thermal conductivity are both conducive to a higher current rating.

Switching

The switching speed of a diode depends upon its construction and fabrication. In general the

smaller the chip the faster it switches, other things being equal. The reverse recovery time, trr, is

usually the limiting parameter; trr is the time it takes a diode to switch from on to off.

Fig 3.3.5: Diode characteristics


IC 7805 &S IC 7812

7805 & 7812 is an integrated three-terminal positive fixed linear voltage regulator. It supports

an input voltage of 10 volts to 35 volts and output voltage of 5 volts. It has a current rating of 1 amp

although lower current models are available. Its output voltage is fixed at 5.0V. The 7805 also has a

built-in current limiter as a safety feature. 7805 is manufactured by many companies, including

National Semiconductors and Fairchild Semiconductors.

The 7805 will automatically reduce output current if it gets too hot.The last two digits

represent the voltage; for instance, the 7812 is a 12-volt regulator. The 78xx series of regulators is

designed to work in complement with the 79xx series of negative voltage regulators in systems that

provide both positive and negative regulated voltages, since the 78xx series can't regulate negative

voltages in such a system.

The 7805 & 7812 is one of the most common and well-known of the 78xx series regulators, as its

small component count and medium-power regulated 5V make it useful for powering TTL devices.

SPECIFICATIONS IC 7805 IC 7812

Vout 5V 12V

Vin - Vout Difference 5V - 20V 5V - 20V

Operation Ambient Tmp 0 - 125°C 0 - 125°C

Output Imax 1A 1A


3.4 Switching Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and

power. It is composed of a semiconductor material with at least three terminals for connection to an

external circuit. A voltage or current applied to one pair of the transistor's terminals changes the

current flowing through another pair of terminals. Because the controlled (output) power can be much

more than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are

packaged individually, but many more are found embedded in integrated circuits.

The Transistor as a Switch

When used as an AC signal amplifier, the transistors Base biasing voltage is applied in such a

way that it always operates within its "active" region, that is the linear part of the output characteristics

curves are used. However, both the NPN & PNP type bipolar transistors can be made to operate as

"ON/OFF" type solid state switches by biasing the transistors base differently to that of a signal

amplifier. Solid state switches are one of the main applications for the use of transistors, and transistor

switches can be used for controlling high power devices such as motors, solenoids or lamps, but they

can also used in digital electronics and logic gate circuits.

If the circuit uses the Bipolar Transistor as a Switch, then the biasing of the transistor, either NPN or

PNP is arranged to operate the transistor at both sides of the I-V characteristics curves we have seen

previously. The areas of operation for a transistor switch are known as the Saturation Region and the

Cut-off Region. This means then that we can ignore the operating Q-point biasing and voltage divider

circuitry required for amplification, and use the transistor as a switch by driving it back and forth

between its "fully-OFF" (cut-off) and "fully-ON" (saturation) regions as shown below.


Operating regions

Fig 3.4.1: Operating regions of transistor

The pink shaded area at the bottom of the curves represents the "Cut-off" region while the blue

area to the left represents the "Saturation" region of the transistor. Both these transistor regions are

defined as:

1. Cut-off Region

Here the operating conditions of the transistor are zero input base current ( IB ), zero output

collector current ( IC ) and maximum collector voltage ( VCE ) which results in a large depletion layer

and no current flowing through the device. Therefore the transistor is switched "Fully-OFF".


Cut-off Characteristics

Fig 3.4.2: Cut-off characteristics

The input and Base are grounded (0v)

Base-Emitter voltage VBE < 0.7V

Base-Emitter junction is reverse biased

Base-Collector junction is reverse biased

Transistor is "fully-OFF" (Cut-off region)

No Collector current flows ( IC = 0 )

VOUT = VCE = VCC = "1"

Transistor operates as an "open switch"

Then we can define the "cut-off region" or "OFF mode" when using a bipolar transistor as a switch as

being, both junctions reverse biased, IB < 0.7V and IC = 0. For a PNP transistor, the Emitter potential

must be negative with respect to the Base.

2. Saturation Region

Here the transistor will be biased so that the maximum amount of base current is applied, resulting in

maximum collector current resulting in the minimum collector emitter voltage drop which results in

the depletion layer being as small as possible and maximum current flowing through the transistor.

Therefore the transistor is switched "Fully-ON".


Saturation Characteristics

Fig 3.4.3: Saturation Characteristics

The input and Base are connected to VCC

Base-Emitter voltage VBE > 0.7V

Base-Emitter junction is forward biased

Base-Collector junction is forward biased

Transistor is "fully-ON" (saturation region)

Max Collector current flows (IC = Vcc/RL)

VCE = 0 (ideal saturation)

VOUT = VCE = "0"

Transistor operates as a "closed switch

Then we can define the "saturation region" or "ON mode" when using a bipolar transistor as a switch

as being, both junctions forward biased, IB > 0.7V and IC = Maximum. For a PNP transistor, the

Emitter potential must be positive with respect to the Base.

Then the transistor operates as a "single-pole single-throw" (SPST) solid state switch. With a zero

signal applied to the Base of the transistor it turns "OFF" acting like an open switch and zero collector

current flows. With a positive signal applied to the Base of the transistor it turns "ON" acting like a

closed switch and maximum circuit current flows through the device.

An example of an NPN Transistor as a switch being used to operate a relay is given below. With

inductive loads such as relays or solenoids a flywheel diode is placed across the load to dissipate the

back EMF generated by the inductive load when the transistor switches "OFF" and so protect the


transistor from damage. If the load is of a very high current or voltage nature, such as motors, heaters

etc, then the load current can be controlled via a suitable relay as shown.

3.5 CMOS Decade counter

Description

CD4017B and CD4022B are 5-stage and 4-stage Johnson counters having 10 and 8 decoded

outputs, respectively. Inputs include a CLOCK, a RESET, and a CLOCK INHIBIT signal. Schmitt

trigger action in the CLOCK input circuit provides pulse shaping that allows unlimited clock input

pulse rise and fall times.

These counters are advanced one count at the positive clock signal transition if the CLOCK INHIBIT

signal is low. Counter advancement via the clock line is inhibited when the CLOCK INHIBIT signal is

high. A high RESET signal clears the counter to its zero count. Use of the Johnson counter

configuration permits high-speed operation, 2-input decode-gating and spike-free decoded outputs.

Anti-lock gating is provided, thus assuring proper counting sequence.

Features

Fully static operation

Medium speed operation…10 MHz (typ.) at VDD = 10 V

Standardized, symmetrical output characteristics

100% tested for quiescent current at 20 V

5-V, 10-V, and 15-V parametric ratings

Meets all requirements of JEDEC Tentative Standard No. 13B, "Standard Specifications

for Description of ’B’ Series CMOS Devices"


Decade counter/decimal decode display (CD4017B)

Binary counter/decoder

Frequency division

Counter control/timers

Divide-by-N counting

For further application information, see ICAN-6166 "COS/MOS MSI Counter and Register

Design and Applications

Operation

The 4017 operates very simply. For each pulse on the clock input pin is turns the currently

high output low and makes the next output high. When the 10th Output is high and a pulse is received,

the 10th output goes low and the 1st output goes high and the sequence begins again. The 4017 also has

two other inputs. The first in a Reset Pin. On a rising edge this resets the 4017 to the first output. The

last input is a disable pin, labeled as an enable pin with a circle on the input (the dot means ‘not’).

When this pin is high the 4017 will not advance to the next output but the reset pin is still active.

The 4017 has 11 outputs. There are the regular 10 outputs and a carry out that outputs a pulse when 10

is the current high output and a pulse on the clock pin is received. If your application requires counting

to a number less than 10, you can feed the first unused output in to the reset pin. (i.e. If counting to 7

feed the 8th output into the reset pin)

Writing notes and Suggestions

The pins I call outputs 1-10 are usually labeled 0-9.


There are a number of things you can do to make things work better. First place a capacitor

across the power and ground leads of the chip as close to the chip as you can. (You should do this with

every chip you use.) Tie all unused inputs to ground. Connect all used inputs to ground with a 4.7k_

resistor. This will keep the chip from doing strange things if a signal lead get disconnected. If which

output is on at a giving time is important, you should send a reset signal to the stamp when the first

output should be high. This will do nothing if the first output is high and it will make the first output

high if the count has gone wrong for some reason. If you are counting to a number less than 10 and

sending a reset from the stamp, you should use an OR gate to combine the signals before the Reset

pin.

Fig 3.5.1: CMOS Decade Counter

OUTPUTS

The 4017 decade counter provides a logic level output. This can be used in a number of ways. Using

AND gates the output can be combined with another signal, such as a stamp output, to drive only one

device at a time.


Fig 3.5.2: CMOS logic level output

If you are driving a large load such that you do not want to build or buy multiple drivers, (For example

you want to sequence a bunch of lights that are all dimmed with a dimmer.) you can drive relays with

the output of 4017 and the relays connect the device to the driver.

Fig 3.5.3: Driving CMOS to Relays

3.6 RELAY

A relay is an electrical switch that opens and closes under control of another electrical circuit.

In the original form, the switch is operated by an electromagnet to open or close one or many sets of

contacts. It was invented by Joseph Henry in 1835. Because a relay is able to control an output circuit

of higher power than the input circuit, it can be considered, in a broad sense, to be a form of electrical

amplifier.


A type of relay that can handle the high power required to directly control an electric motor or

other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead

using a semiconductor device to perform switching. Relays with calibrated operating characteristics

and sometimes multiple operating coils are used to protect electrical circuits from overload or faults;

in modern electric power systems these functions are performed by digital instruments still called

"protective relays".

Operation

When a current flows through the coil, the resulting magnetic field attracts an armature that is

mechanically linked to a moving contact. The movement either makes or breaks a connection with a

fixed contact. When the current to the coil is switched off, the armature is returned by a force

approximately half as strong as the magnetic force to its relaxed position. Usually this is a spring, but

gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate

quickly. In a low voltage application, this is to reduce noise. In a high voltage or high current

application, this is to reduce arcing.

If the coil is energized with DC, a diode is frequently installed across the coil, to dissipate the

energy from the collapsing magnetic field at deactivation, which would otherwise generate a spike of

voltage and might cause damage to circuit components. If the coil is designed to be energized with

AC, a small copper ring can be crimped to the end of the solenoid. This "shading ring" creates a small

out-of-phase current, which increases the minimum pull on the armature during the AC cycle.

By analogy with the functions of the original electromagnetic device, a solid-state relay is

made with a thyristor or other solid-state switching device. To achieve electrical isolation, a light-

emitting diode (LED) is used with a photo transistor.

The contacts can be either Normally Open (NO), Normally Closed (NC), or change-over (CO)

contacts.

Normally-open contacts connect the circuit when the relay is activated; the circuit is

disconnected when the relay is inactive. It is also called Form A contact or "make" contact.

Form A contact is ideal for applications that require to switch a high-current power source

from a remote device.

Normally-closed contacts disconnect the circuit when the relay is activated; the circuit is

connected when the relay is inactive. It is also called Form B contact or "break" contact. Form


B contact is ideal for applications that require the circuit to remain closed until the relay is

activated.

Selection of an appropriate relay for a particular application requires evaluation of many

different factors:

Number and type of contacts - normally open, normally closed, changeover (double-throw)

In the case of changeover, there are two types. This style of relay can be manufactured two

different ways. "Make before Break" and "Break before Make". The old style telephone switch

required Make-before-break so that the connection didn't get dropped while dialing the

number. The railroad still uses them to control railroad crossings.

Rating of contacts - small relays switch a few amperes, large contactors are rated for up to

3000 amperes, alternating or direct current

Voltage rating of contacts - typical control relays rated 300 VAC or 600 VAC, automotive

types to 50 VDC, special high-voltage relays to about 15,000 V

Coil voltage - machine-tool relays usually 24 VAC or 120 VAC, relays for switchgear may

have 125 V or 250 VDC coils, "sensitive" relays operate on a few mill amperes

Package/enclosure - open, touch-safe, double-voltage for isolation between circuits, explosion

proof, outdoor, oil-splash resistant.

Mounting - sockets, plug board, rail mount, panel mount, through-panel mount, enclosure for

mounting on walls or equipment

Switching time - where high speed is required

"Dry" contacts - when switching very low level signals, special contact materials may be

needed such as gold-plated contacts

Contact protection - suppress arcing in very inductive circuits


Coil protection - suppress the surge voltage produced when switching the coil current

Isolation between coil circuit and contacts

Aerospace or radiation-resistant testing, special quality assurance

Accessories such as timers, auxiliary contacts, pilot lamps, test buttons

Regulatory approvals

Types of RELAY

Latching relay

A latching relay has two relaxed states (bistable). These are also called "impulse", "keep", or

"stay" relays. When the current is switched off, the relay remains in its last state. This is achieved with

a solenoid operating a ratchet and cam mechanism, or by having two opposing coils with an over-

center spring or permanent magnet to hold the armature and contacts in position while the coil is

relaxed, or with a remnant core. In the ratchet and cam example, the first pulse to the coil turns the

relay on and the second pulse turns it off. In the two coil example, a pulse to one coil turns the relay on

and a pulse to the opposite coil turns the relay off. This type of relay has the advantage that one coil

consumes power only for an instant, while it is being switched, and the relay contacts retain this

setting across a power outage. A remnant core latching relay requires a current pulse of opposite

polarity to make it change state.

Reed relay

A reed relay is a reed switch enclosed in a solenoid.


The switch has a set of contacts inside an evacuated or inert gas-filled glass tube which

protects the contacts against atmospheric corrosion; the contacts are made of magnetic material that

makes them move under the influence of the field of the enclosing solenoid. Reed relays can switch

faster than larger relays, require only little power from the control circuit, but have low switching

current and voltage ratings. In addition, the reeds can become magnetized over time, which makes

them stick 'on' even when no current is present; changing the orientation of the reeds with respect to

the solenoid's magnetic field will fix the problem.

Polarized relay

A polarized relay placed the armature between the poles of a permanent magnet to increase sensitivity.

Polarized relays were used in middle 20th Century telephone exchanges to detect faint pulses and

correct telegraphic distortion. The poles were on screws, so a technician could first adjust them for

maximum sensitivity and then apply a bias spring to set the critical current that would operate the

relay.

Contactor relay

A contactor is a very heavy-duty relay used for switching electric motors and lighting loads,

although contactors are not generally called relays. Continuous current ratings for common contactors

range from 10 amps to several hundred amps. High-current contacts are made with alloys

containing silver. The unavoidable arcing causes the contacts to oxidize; however, silver oxide is still

a good conductor. Such devices are often used for motor starters. A motor starter is a contactor with

overload protection devices attached. The overload sensing devices are a form of heat operated relay

where a coil heats a bi-metal strip, or where a solder pot melts, releasing a spring to operate auxiliary

contacts. These auxiliary contacts are in series with the coil. If the overload senses excess current in

the load, the coil is de-energized. Contactor relays can be extremely loud to operate, making them

unfit for use where noise is a chief concern.

Solid-state relay

A solid state relay (SSR) is a solid state electronic component that provides a similar function

to an electromechanical relay but does not have any moving components, increasing long-term

reliability. With early SSR's, the tradeoff came from the fact that every transistor has a small voltage

drop across it. This voltage drop limited the amount of current a given SSR could handle. The


minimum voltage drop for such a relay is equal to the voltage drop across one transistor (~0.6-2.0

volts), and is a function of the material used to make the transistor (typically silicon). As transistors

improved, higher current SSR's, able to handle 100 to 1,200 Amperes, have become commercially

available. Compared to electromagnetic relays, they may be falsely triggered by transients.

Overload protection relay

Electric motors need over current protection to prevent damage from over-loading the motor,

or to protect against short circuits in connecting cables or internal faults in the motor windings. One

type of electric motor overload protection relay is operated by a heating element in series with

the electric motor. The heat generated by the motor current heats a bimetallic strip or melts solder,

releasing a spring to operate contacts. Where the overload relay is exposed to the same environment as

the motor.

3.7 RELAY DRIVER CIRCUIT

One of the serious problems in relay operated circuits is the relay clicking or chattering during

the on/off of the relay driver transistor. This problem is severe if the input circuit is a light /

temperature sensor. During the transition of light / temperature levels, the relay clicks which may

cause sparking of contacts. By using a simple tip, this problem can be avoided.

Below is the circuit of a Relay driver using the NPN transistor BC 548. The relay is connected

between the positive rail and the collector of the transistor. When the input signal passes through the I

K resistor to the base of the transistor, it conducts and pulls the relay. By adding a 470 uF electrolytic

capacitor at the base of the relay driver transistor, a short lag can be induced so that the

transistor switches on only if the input signal is persisting. Again, even if the input signal ceases, the

transistor remains conducting till the capacitor discharges completely. This avoids relay clicking and

the offers clean switching of the relay.


Fig 3.7.1: Relay Driver circuit

Another 470 uF capacitor is added parallel to the relay coil which maintains steady current

through the relay coil so that relay clicking can be avoided if the power supply varies momentarily.

IN 4007 diode eliminates back e.m.f when the relay switches off and protects the transistor. LED

indicates the on status of the relay.

3.8 POWER SUPPLY

The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V

from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output

obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage, the output

voltage from the rectifier is fed to a filter to remove any a.c components present even after

rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.

230V AC

50HzD.C

Output


Fig 3.8.1: Power supply

Transformer

Usually, DC voltages are required to operate various electronic equipment and these voltages

are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the

mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a

transformer. Thus, a step down transformer is employed to decrease the voltage to a required level.

Rectifier:

The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The

rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of

its merits like good stability and full wave rectification.

Filter

Capacitive filter is used in this project. It removes the ripples from the output of rectifier and

smoothens the D.C. Output received from this filter is constant until the mains voltage and load is

maintained constant. However, if either of the two is varied, D.C. voltage received at this point

changes. Therefore a regulator is applied at the output stage.

Voltage regulator

As the name itself implies, it regulates the input applied to it. A voltage regulator is an

electrical regulator designed to automatically maintain a constant voltage level. In this project, power

supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812 voltage

RegulatorFilter

Bridge

Rectifier

Step down

transformer


regulators are to be used. The first number 78 represents positive supply and the numbers 05, 12

represent the required output voltage levels.

Necessity of regulated power supply:

The DC level of an ordinary power supply changes due to the following reasons. Variations in

AC mains voltage: the permissible variation in the mains voltage as per Indian electricity rules is +/-

6% of its rated value. But in India the variation in voltage is much more than its rated value. That is

why the DC voltage of an ordinary power supply changes to such an extent that the electronic device

refuses to work satisfactorily. Voltages drop in internal resistance: the internal resistance of an

ordinary power supply is very large. Therefore output voltage changes to an extent when load is

connected across it. Some it reduces to very low extent due to which the electronic component refuses

to work.

Transformer

A transformer is an electrical device that transfers energy from one circuit to another by

magnetic coupling with no moving parts. A transformer comprises two or more coupled windings, or a

single tapped winding and, in most cases, a magnetic core to concentrate magnetic flux. A changing

current in one winding creates a time-varying magnetic flux in the core, which induces a voltage in the

other windings.

Basic principles

A simple transformer consists of two electrical conductors called the primary winding and the

secondary winding. Energy is coupled between the windings by the time-varying magnetic flux that

passes through (links) both primary and secondary windings. Whenever the amount of current in a coil

changes (including when the current is switched on or off), a voltage is induced in the neighboring

coil. The effect, called mutual inductance, is an example of electromagnetic induction.

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Fig 3.8.2

If a time-varying voltage is applied to the primary winding of

flow in it producing a magneto motive force (MMF). Just as an

current around an electric circuit, so MMF tries to drive magnetic flux through a magnetic circuit.

The primary MMF produces a varying magnetic flux

circuit secondary winding, induces a back

accordance with Faraday's law of induction, the voltage induced across the primary winding is

proportional to the rate of change of flux:

and

Where vP and vS are the voltages across the primary

NP and NS are the numbers of turns in the primary winding and secondary winding,

dΦP / dt and dΦS / dt are the derivatives of the flux with respect to time of the primary and secondary

windings.

Saying that the primary and secondary windings are perfectly coupled is equivalent to saying that

. Substituting and solving for the voltages shows that:


Fig 3.8.2: Transformer

is applied to the primary winding of turns, a current will

flow in it producing a magneto motive force (MMF). Just as an electromotive force (EMF) drives


The primary MMF produces a varying magnetic flux in the core, and, with an open

circuit secondary winding, induces a back electromotive force (EMF) in opposition to


vP and vS are the voltages across the primary winding and secondary winding,

NP and NS are the numbers of turns in the primary winding and secondary winding,


d secondary windings are perfectly coupled is equivalent to saying that

. Substituting and solving for the voltages shows that:

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turns, a current will

electromotive force (EMF) drives


in the core, and, with an open

electromotive force (EMF) in opposition to . In



d secondary windings are perfectly coupled is equivalent to saying that


Where vp and vs are voltages across primary and secondary,

Np and Ns are the numbers of turns in the primary and secondary, respectively.

Hence in an ideal transformer, the ratio of the primary and secondary voltages is equal to the

ratio of the number of turns in their windings, or alternatively, the voltage per turn is the same for both

windings.

Transformer losses arise from:

Winding resistance

Current flowing through the windings causes resistive heating of the conductors (I2 R loss). At

higher frequencies, skin effect and proximity effect create additional winding resistance and losses.

Eddy currents

Induced eddy currents circulate within the core, causing resistive heating. Silicon is added to

the steel to help in controlling eddy currents. Adding silicon also has the advantage of stopping aging

of the electrical steel that was a problem years ago.

Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost to hysteresis within

the magnetic core. The amount of hysteresis is a function of the particular core material.

Magnetostriction

Magnetic flux in the core causes it to physically expand and contract slightly with the

alternating magnetic field, an effect known as magnetostriction. This in turn causes losses due to

frictional heating in susceptible ferromagnetic cores.

Mechanical losses

In addition to magnetostriction, the alternating magnetic field causes fluctuating

electromagnetic forces between the primary and secondary windings. These incite vibrations within

nearby metalwork, creating a familiar humming or buzzing noise, and consuming a small amount of

power.

Stray losses


Not all the magnetic field produced by the primary is intercepted by the secondary. A portion

of the leakage flux may induce eddy currents within nearby conductive objects, such as the

transformer's support structure, and be converted to heat.

4. WORKING

CD4017 is a CMOS Decade counter. It can detect a clock pulse and the BCD output will be

incremented by one for each CLK pulse. If we observe the BCD numbers, the LSB (Least Significant

Bit) of BCD complemented every time. This project uses this LSB to switch ON / OFF an electrical

appliance.

TSOP1738 is a high sensitive IR receiver which can sense 38 KHz IR light. The electrolytic

capacitor (100μF) connected across pin no’s 3 and 1 of TSOP1738 for medium sensitivity. The NPN

transistor BC557 is connected as a switch. Whenever an IR signal is detected, the transition is sensed

by the PNP transistor and it supplies a CLK pulse to the BCD counter (CD4017). For every clock

pulse the LSB (Least Significant Bit) of the BCD output is complemented. This toggling output is

given to an NPN transistor through a base resistor.

If logic ‘0’ is applied to the transistor, it will be driven into cut-off region. As the collector

current is zero in cut-off region, the relay will not be energized and the electrical appliance will be in

OFF mode.

If logic ‘1’ is applied to the transistor, it will be driven into saturation region. As the collector

current is high in saturation region, the relay will be energized and the electrical appliance will be in

ON mode. A diode is connected across the relay to protect the transistor by neutralizing the reverse

EMF generated by the electromagnetic relay. An LED connected at pin no.2 of CD4017 to indicate the

ON condition of the LOAD. An LED connected at pin no.3 of CD4017 to indicate the OFF condition

of the LOAD.


5. USAGE

Industry

Remote control is used for controlling substations, pump storage power stations

and HVDC-plants. For these systems often PLC-systems working in the long range are used.

Military

Only in the military field of use of remote controls can you find the jammers and the counters

measures against the jammers. Jammers are used to disable or sabotage the enemy’s use of remote

controls. IED jamming systems, Radio jamming, Electronic warfare the distances for military remote

controls also tend to be much longer, up to intercontinental distance satellite linked remote controls

used by the U.S. for their unmanned airplanes (drones) in Afghanistan, Iraq and Pakistan.

Remote controls are used by insurgents in Iraq and Afghanistan to attack coalition and

government troops with roadside IED’s (Improved explosive device, explosively formed penetrator).

The arms race and the fact that the enemy is many times closer to the receiver has made it made more

complicated and too expensive to build radio remote controls for road side bombs that are immune to

jammers. The simplest types of radio remote controls have been almost entirely disabled by the

advanced jammers, but are still in use against unprotected Iraqi and afghan national troops and civilian

targets. One of the simplest solutions against the radio jammers itself to ignite the bomb.

Optical types of remote controls that use light instead of radio are still immune to the jammers.

The resistance in Iraq is reported in the media to use modified TV remote controls to detonate the

bombs.

Military history

In the World War I, the imperial German Navy employed FL-boats (Fernlenkboote) against

coastal shipping. These were driven by internal combustion engines, and controlled remotely from a


shore station through several miles of wire wound on a spool on the boat. An aircraft was used to

signal directions to the shore station. EMBs carried a high explosive charge in the bow and travelled at

speeds of thirty knots.

The soviet red army used remotely controlled teletanks during 1930s in the winter war against

Finland and the early stages of world war tank at a distance of 500-1500 meters, the two constituting a

telemechanical group. The Red Army fielded at least two teletanks battalions at the beginning of the

great patriotic war. These were also remotely controlled cutters and experimental remotely planes in

the Red Army.

Space

Remotely control technology is also used in travel, for instance the Russian Lunokhed

vehicles were remote-controlled from the ground. Direct remote control of space vehicles at greater

distance from the earth is not practical due to increasing delay times.

Video games

Video game consoles had not used wireless controllers until recently, mainly because of the

difficulty involved in playing the game while keeping the infrared transmitter pointed at the console.

Early wireless controllers were cumbersome and when powered on alkaline batteries, lasted only a few

hours before they needed replacement. Some wireless controllers were produced by third parties, in

most cases using a radio link instead of infrared. Even these were very inconsistent, and in some cases,

had transmission delays, making them virtually useless. The first official wireless controller made by a

first party manufacturer was the wave bird for Nintendo GameCube. The wave bird changed the face

of wireless technology in video game consoles. In the current generation of gaming consoles, wireless

controllers have become the standard.

PC control

Existing infrared remote controls can be to control PC applications. Any application that

supports shortcut keys can be controlled via IR remote controls from other home devices (TV, VCR,

AC …). This is widely used with multimedia applications for PC based Home Theatre systems. For

this to work, you need a device that decodes IR remote control data signals and a PC. Connection can

be made via serial port, USB port or motherboard IrDA connector. Such devices are commonly

available or it can be home made using low cost microcontrollers.


LIRC (Linux IR Remote Control) and Win-LIRC(for Windows) software are developed for the

controlling PC using TV remote and can also used for home brew remote with lesser modification.

They support almost all TV remotes. Examples of many PC remote controls circuits are available here.

Almost everybody today is used to operating a remote control. From the TV, to the DVD

player, up to the air conditioner, there are just a few appliances left without their own remote control.

The home apparatus are motor, refrigerator, TV, FANS AND A/C. these all apparatus are

controlled by PC. This project has communication levels one is receiving end another one is

transmitting part. In the transmitter circuit already defined control data’s were loaded in the Controller.

When we need to control a device we should enter the device number in computer from HYPERLINK

TEMINAL. The number is transferred from pc to Controller read the data’s, it will generate the

control signal and send it to Corresponding circuit. When the specific device sensed the signal for that

it will decoded and given to the controller. Then the controller generates the control signal based upon

the received signal and gives it to the unit to control the device.

6. ADVANTAGES

Highly sensitive

Works with any TV/DVD Remote


Cost and reliable circuit

Coverage distance up to 10m

Can handle heavy loads up to 7A

System can be switched into manual mode whenever required

7. APPLICATIONS

Home appliance control

Hotel lights/fans control


Shops and showrooms

Industrial applications

Electronic toys

8. CONCLUSION

The project “ELECTRICAL APPLIANCE CONTROL USING TVREMOTE” has been

successfully designed and tested. It has been developed by integrating features of all the hardware

components used. Presence of every module has been reasoned out placed carefully thus contributing

to the best working of the unit.


Secondly, using highly advanced IC’s and with the help of growing technology the project has

been successfully implemented.

controling electrical appliances through tv remote

Education